The present invention relates to an arrangement for cleaning the circumferential surface of a pressure roller of a pair of delivery rollers of a drafting unit of a spinning machine, having a suction device assigned to the circumferential surface of the pressure roller.
In the case of an arrangement of the initially mentioned type (German Patent Document DE-OS 15 10 603), the suction device has the purpose of providing that the pressure roller of the pair of delivery rollers will be cleaned continuously during the normal spinning operation, and that, after a yarn breakage, a lap formation is prevented on the pair of delivery rollers. In particular, for the latter purpose, a relatively strong vacuum is necessary so that this arrangement has a relatively high energy requirement.
It is also known (German Patent Document DE 39 24 568 A1) to mount a suction nozzle on a servicing carriage that can be moved along a spinning machine, which suction nozzle is applied during a servicing operation to an area between a delivery roller pair of a drafting unit and a twisting element which follows, and cleans this area.
The invention is based on the object of developing an arrangement of the initially mentioned type such that only a reduced energy requirement is necessary without limiting the operatability.
This object is achieved in that devices are provided for reinforcing the cleaning effect during a restarting of the drafting unit after a stoppage.
The invention is based on the recognition that, during the normal spinning operation, only relatively low cleaning forces, particularly suction forces, are required in order to keep the pressure roller clean. This increased cleaning effect is provided only when it is actually required, specifically during the restarting of the drafting unit after a stoppage. As a result, it is possible to clearly reduce the energy consumption since only the actually required energy needs to be use up.
In the case of an expedient development of the invention, it is provided that the suction device, during the restarting of the drafting unit, can be operated with an increased vacuum. In a further development, it is provided in this case that two suction nozzles are assigned to the pressure roller of the pair of delivery rollers, one of the suction nozzles being drivable with an increased vacuum. As a result, a simplified switching is achieved which does not require throttle valves or the like.
In a further development of the invention, it is provided that the suction nozzle which can be driven with the stronger vacuum is held so that it can be applied to the pressure roller. In this case, it is particularly advantageous for the applicable suction nozzle to be arranged in a servicing carriage which can be moved along the spinning machine. For increasing the cleaning effect, this suction nozzle will then be applied to the corresponding spinning point during a piecing operation of the pressure roller of the drafting unit.
The invention can particularly advantageously be used in the case of spinning machines in which the drafting units are stopped when a yarn breakage occurs. The wind-around spinning machine "Parafil 2000" manufactured by Spindelfabrik Sussen, is, for example, equipped with drafting units of this type. In the case of this spinning machine, a load carrier with the pressure rollers is swivelled away from the bottom cylinders in the case of a yarn breakage. Likewise, spinning machines are known in which autonomous drafting units are provided for each spinning point which can be stopped individually. It was found that in such cases the coverings of the pressure rollers fall relatively fast from their operating temperature to the ambient temperature. In this case, the phenomenon will then occur that the colder coverings have a higher adhesive effect with respect to the fibers so that the danger of lap formations after the start exists to an increased extent in these cases.
In order to reduce, particularly in the case of drafting units that can be stopped after a yarn breakage, the danger of lap formation from the start and thus lower the required cleaning effect, devices for the heating of the pressure rollers that can be switched on and off are provided as a further development of the invention. As a result, it is possible to heat the pressure roller such that the operational adhering forces exist so that then also the operational cleaning effects are sufficient. In an expedient development of the invention, it is provided in this case that the devices for the heating of the pressure roller are arranged in a servicing carriage which can be moved along the spinning machine. Since this servicing carriage, as a rule, carries out the piecing operation, it will then be sufficient to provide the devices for the heating only once. In a simple embodiment of the invention, at least one nozzle which blows out heated air or the like is provided as the device for the heating.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.